A hydrogel binder and a free-standing electrode

Abstract

There is provided a hydrogel binder and a method of synthesizing the same. There is also provided a free-standing electrode comprising the hydrogel binder and a method of preparing the free-standing electrode comprising the hydrogel binder. There is further provided a battery comprising the free-standing electrode as defined herein.

What is claimed is: 
     
         1 . A hydrogel binder comprising an anionic polyacid, a cationic polyamine and a solvent, wherein the anionic polyacid and the cationic polyamine are derived from an acid-base reaction between a polyacid and a polyamine at a weight ratio in the range of 10:100 to 40:100. 
     
     
         2 . The hydrogel binder of  claim 1 , wherein the weight ratio of the polyacid and the polyamine is 24:100. 
     
     
         3 . The hydrogel binder of  claim 1 , wherein the polyacid is alginic acid or a salt thereof, the polyamine is polyethyleneimine or a salt thereof and the solvent is an aqueous medium. 
     
     
         4 . A method of synthesizing a hydrogel binder comprising mixing a polyacid with a polyamine at a weight ratio in the range of 10:100 to 40:100 in a solvent. 
     
     
         5 . The method of  claim 4 , wherein the weight ratio of the polyacid and the polyamine is 24:100. 
     
     
         6 . The method of  claim 4 , wherein the polyacid is alginic acid or a salt thereof, the polyamine is polyethyleneimine or a salt thereof and the solvent is an aqueous medium. 
     
     
         7 . A free-standing electrode comprising a hydrogel binder and carbon nanotubes, wherein the hydrogel binder comprises an anionic polyacid and a cationic polyamine, wherein the anionic polyacid and the cationic polyamine are derived from an acid-base reaction between a polyacid and a polyamine at a weight ratio in the range of 10:100 to 40:100. 
     
     
         8 . The free-standing electrode of  claim 7 , wherein the weight ratio of the polyacid and the polyamine is 24:100. 
     
     
         9 . The free-standing electrode of  claim 7 , wherein the polyacid is alginic acid or a salt thereof, and the polyamine is polyethyleneimine or a salt thereof. 
     
     
         10 . The free-standing electrode of  claim 7 , further comprising a conductive additive selected from the group consisting of graphene, graphene oxide, reduced graphene oxide, carbon fiber, carbon black and combinations thereof. 
     
     
         11 . The free-standing electrode of  claim 7 , further comprising an active electrode material selected from the group consisting of transition metal oxides, phosphate salts of lithium and a transition metal, metalloids and combinations thereof. 
     
     
         12 . A method of preparing a free-standing electrode comprising the steps of:
 a) mixing a hydrogel binder and carbon nanotubes in a mixing solvent to form a slurry, wherein the hydrogel binder comprises an anionic polyacid and a cationic polyamine, and wherein the anionic polyacid and the cationic polyamine are derived from an acid-base reaction between a polyacid and a polyamine in a weight ratio in the range of 10:100 to 40:100 and a solvent; and   b) casting and drying the slurry of step (a) on a substrate to form the free-standing electrode.   
     
     
         13 . The method of  claim 12 , wherein in step (a), the weight ratio of the polyacid and the polyamine is 24:100. 
     
     
         14 . The method of  claim 12 , wherein in step (a), the polyacid is alginic acid or a salt thereof, the polyamine is polyethyleneimine or a salt thereof and the solvent is an aqueous medium. 
     
     
         15 . The method of  claim 12 , wherein in step (a), the mixing solvent is a mixture of N-methyl-2-pyrrolidone and water at a volume ratio of 1:1. 
     
     
         16 . The method of  claim 12 , wherein the mixing step (a) further comprises mixing the slurry with a conductive additive selected from the group consisting of graphene, graphene oxide, reduced graphene oxide, carbon fiber, carbon black and combinations thereof. 
     
     
         17 . The method of  claim 12 , wherein the mixing step (a) further comprises mixing the slurry with an active electrode material selected from the group consisting of transition metal oxides, phosphate salts of lithium and a transition metal, metalloids and combinations thereof. 
     
     
         18 . The method of  claim 12 , wherein the mixing step (a) is undertaken by ball milling and/or stirring. 
     
     
         19 . A battery comprising the free-standing electrode of  claim 7 , a sulfur source, a separator and an electrolyte. 
     
     
         20 . A battery comprising at least one free-standing electrode of  claim 11 , a separator and an electrolyte.